What are Prokaryotes?

Prokaryotes refer to a class of primitive single-celled organisms that have no nuclear membrane envelope and only naked DNA called the nuclear region. It includes bacteria, actinomycetes, rickettsia, chlamydia, mycoplasma, cyanobacteria and archaea. They are all single-celled prokaryotes with simple structures ^[1] and small individuals, usually 1 to 10 µm, which are only one-tenth to one ten-thousandth of the eukaryotic cells. ^[2]

Prokaryotes are bacteria in a broad sense. They refer to a large class of nuclear-free membrane-encapsulated primitive single-celled organisms with bare DNA called nuclear regions, including two groups of true bacteria and archaea. The characteristics of many eukaryotes are clearly different from bacteria, so archaea are not included in it, and they are described separately. Prokaryotes can be specifically classified into seven categories: bacteria, cyanobacteria, actinomycetes, mycoplasma, chlamydia, spirochaete, and rickettsial organisms according to their external characteristics. ^[3]

Prokaryotes still have the basic structure of cells and contain cytoplasm, cell walls, cell membranes, and

Although it is incomplete and simple, it can have long-term survival in this highly competitive environment with its own unique skills: the diversity of prokaryotes. Such as the diversity of cell morphology, the diversity of movement, the diversity of growth and development, the diversity of cell structure, the diversity of cytochemistry, the diversity of metabolic functions, and the diversity of genetic variation. Therefore, it is a biological resource with extremely high utilization value. This resource is not only represented by the infinite metabolic functional traits of almost all organisms that are closely related to human existence, but also a colorful microbial world. ^[4]

None between nuclear and cytoplasm

Prokaryote cells can carry on

Prokaryote

For a long time, it was thought that the cytoskeleton was only

Viruses (animal viruses such as

Microbes are extremely widespread in nature. There are various types and types of microorganisms in soil, air, rivers, and oceans. Among them, soil has the most microorganisms. A variety of microorganisms exist on the human body, the surface of animals and plants, and the luminal passages that communicate with the outside world, such as the respiratory tract and digestive tract. Under normal circumstances, the microorganisms living on the surface of the human body and in communication with the external cavity such as the oral cavity, nasopharynx, intestine and urogenital tract are called "normal flora".

The majority of microorganisms in nature are beneficial and necessary for human flora and fauna. For example, microorganisms in the soil can convert the organic proteins of plants and animals into inorganic nitrogen compounds for the needs of plant growth, and plants are eaten by humans and animals. A large amount of nitrogen in the air can be absorbed by plants only by the role of nitrogen-fixing bacteria. E. coli in the intestine can synthesize vitamin B and vitamin K, which are used by the body and have the effect of antagonizing certain pathogenic bacteria. The widely used antibiotics are metabolites of microorganisms and are used to treat various acute and chronic infectious diseases. The relationship between microbes and humans is extremely close.

In addition to some microorganisms that are beneficial to humans in nature, there are also some that can cause human and animal and plant diseases. These pathogenic microorganisms are called "pathogenic microorganisms". For example, it can cause human dysentery, typhoid fever, tuberculosis, viral hepatitis, and can cause chicken cholera, duck blast, and rice leaf blight on animals and plants.

Pathogenic microorganisms can be divided into three types: the first is non-cellular microorganisms: viruses belong to this type of microorganisms. Its small size does not have typical cells

Food poisoning caused by prokaryotes

Structure, no enzyme system that produces energy, can only grow and reproduce in living cells of the host. The second category is prokaryotic cell-type microorganisms: these microorganisms have only nucleoplasm, no nuclear membrane or nucleoli, and imperfect organelles, including bacteria, mycoplasma, rickettsia, chlamydia, spirochaete, and actinomycetes. The third category is eukaryotic cell-type microorganisms: these microorganisms have a high degree of nuclear differentiation, with nuclear membranes, nucleoli and chromosomes, and complete organelles in the cytoplasm. Fungi belong to this group of microorganisms.

Gram staining can be used to classify all bacteria into Gram-positive and negative bacteria. This method is the most commonly used conventional staining method. Bacteria are stained with deep purple after crystal violet and iodine staining. At this time, it is decolorized with 95% alcohol. Some bacteria can take off the purple, and then re-stained with fuchsin, and it becomes red. It is called Gram-negative bacteria (abbreviated as G-bacteria). Some bacteria are not decolorized by alcohol and still retain a dark purple color. They are called Gram-positive bacteria (G + bacteria for short).

Distinguishing these two types of bacteria is of great significance in identifying bacteria, analyzing their pathogenic effects, and selecting antibacterial drugs. The preliminary classification of all bacteria into two categories, G + and G-, facilitates further identification of bacterial species; on the other hand, because G + and G- bacteria have different susceptibility to antibiotics, this makes it easier to select effective drugs for timely treatment. G + bacteria are sensitive to penicillin and cephalosporins, while G- bacteria are more sensitive to streptomycin, gentamicin, kanamycin, and chloramphenicol, which can be used as a reference for treatment. The laboratory can still conduct drug sensitivity tests by separating and culturing bacteria to help correctly select effective drugs and achieve the purpose of rationally treating different infectious diseases. In addition, G + bacteria and G- bacteria are different in the pathogenic effect of bacteria. For example, G + bacteria are generally caused by external toxins, while G- bacteria are mainly caused by endotoxins.

Food poisoning is the symptoms of poisoning caused by eating toxic food, including bacterial food poisoning and non-bacterial food poisoning (or toxic food poisoning, such as eating poisonous mushrooms, or pesticides, or containing poisonous foods) Chemical food, etc.).

Bacterial food poisoning (including toxic food poisoning and infectious food poisoning). Except for botulinum toxin produced by botulinum, clinical manifestations of food poisoning caused by other bacteria are symptoms of acute gastrointestinal inflammation, such as abdominal pain, diarrhea, Vomiting is predominant (few with fever). The general symptoms are mild and the prognosis is good. It can heal itself within 1 to 2 days, and few reports have caused death.

Food poisoning caused by bacterial contamination is common in hot summer and autumn. There are a variety of bacteria that can cause food poisoning, the most common of which is Salmonella. It is widely found in the intestines and feces of various animals, such as pigs, cattle, sheep, chickens, ducks, geese and rats, and eggs are also easily contaminated by this fungus. Staphylococcus aureus is also one of the common pathogens that cause food poisoning. It often exists in the nasal cavity, throat and skin suppuration lesions of normal people. Staphylococci are also abundant in cow's breast pustules. Among the food poisoning caused by Staphylococcus aureus, type A causes the most, followed by types B and C.

In addition, Proteus and Bacillus cereus, a variety of seafood, salted products, a kind of Vibrio parahaemolyticus, perfringens in meat foods, fermented beans, pasta products, canned foods, cured meats Botox can cause food poisoning.

We usually see bacterial food poisoning, and the onset is very acute. Most of them can have abdominal pain, diarrhea, vomiting and other symptoms within a few hours after eating unclean food, but they also recover quickly, and can heal in 1 to 2 days. However, there is a toxic food poisoning (generally contaminated by botulinum spores during food processing, and a severe exotoxin produced by bacterial growth and reproduction under anaerobic conditions, called botulinum toxin). This exotoxin food can cause food poisoning. Even if the toxin is only 1 microgram, it can be fatal, so it is the most dangerous "Assassin" in food poisoning.

In foreign countries, such food poisoning is mainly sausages, homemade canned foods, and meat products. However, in China, botulism caused by such foods is rare, and most of them are caused by fermented soybean products and noodle products. Such as stinky tofu, bean drum (80%), sweet noodle sauce (10%) and so on. It has been found in more than a dozen provinces in China, with Xinjiang, Tibet, Qinghai and Ningxia provinces being the most common. Botox can grow only in the absence of oxygen. When it exists in the aerobic environment that is unfavorable to the soil and the feces of livestock, it will produce an oval body, called a spore. In this way, botulinum can survive for a long time. For several years or even decades, if the food is contaminated by botulinum spores during processing, it can grow and reproduce in large quantities under anaerobic conditions, producing highly toxic botulinum toxins. . Because it is a neurotoxin, humans cause special neurotoxic symptoms after ingestion. The paralysis of the eyes and pharynx muscles causes diplopia, strabismus, eye opening, difficulty in eating, and weak chewing. More than 30% of patients have neurons. Can be damaged.

In nature, most pathogenic bacteria cause infection only in humans or animals. But there are also a few animal-derived pathogens that make humans sick. This kind of disease caused by livestock (or wild animals) and humans caused by the same pathogenic bacteria is called zoonotic disease. For example, brucellosis in livestock is mainly pathogenic bacteria of cattle, sheep, pigs and other livestock. After the illness, it manifests as abortion, orchitis, paratestitis, and uterine inflammation. Products, germs can be transmitted to people through the skin, digestive tract, respiratory tract, eye conjunctiva and other ways. Bacteremia occurs, and the fever is wave-shaped, which is called wave fever. Zoonotic diseases can also be caused by Yersinia pestis and Bacillus anthracis. Yersinia pestis is one of the rodent pathogens, and human plague can also occur after being bitten by humans. Bacillus anthracis mainly causes herbivore anthracnose, and can also be transmitted to humans and carnivores, causing human anthrax.